Work machines such as wheel loaders, integrated tool carriers, skid-steer loaders, agricultural tractors, and other work machines have a variety of work tools that may be attachable to the work machine to perform different tasks. These work tools may be hydraulically actuated and require valve assemblies that are in fluid communication with a pump and a tank. When multiple work tools are simultaneously attached to the work machine, fluid communication between the separate valve assemblies and the pump and tank may be difficult and require complex and expensive routing of hydraulic fluid conduits.
One method of reducing the complexity and cost associated with fluidly and simultaneously communicating the multiple work tools with a common pump and tank may include bringing together the separate valve assemblies into a valve stack having a common fluid supply passageway and a common return passageway. The common supply passageway of the valve stack may be fluidly communicated with the pump via a first common hydraulic fluid conduit, while the common return passageway may be fluidly communicated with the tank via a second common hydraulic fluid conduit. One such method is described in U.S. Pat. No. 4,664,220 (the '220 patent) issued to Ruhter et al. on May 12, 1987. The '220 patent describes a stack of functional control valves mounted together in a transverse side-by-side arrangement. Each of the control valves has a hydraulic fitting operably connecting the valve to its respective functional element of a vehicle.
Although the valve stack of the '220 patent may reduce some the complexity and cost involved with fluid communication of multiple control valves, the mounting configuration of these valves may be problematic. For example, as illustrated in FIG. 2 of the '220 patent, the functional control valves are held together by bolts that extend from one side of the stack to the other side of the stack for threaded engagement with nuts, thereby sandwiching the entire stack of control valves between the bolts and nuts. In this configuration, in order to expand the stack by assembling additional control valves to the stack, the entire stack of control valves must be disassembled. Each time the stack of control valves is disassembled, contamination may be introduced into the valve stack, which can shorten component life of the control valves and possibly cause malfunction. In addition, because the entire stack must be taken apart, the process of expansion can be time and labor intensive, and can increase the likelihood of improper assembly.
The disclosed hydraulic valve stack is directed to overcoming one or more of the problems set forth above.